Techniques for balancing voltage across capacitors may be used in several different types of electronic devices including voltage source inverters, multilevel inverters, ultra-capacitors, and capacitor banks. Multilevel inverters provide an output waveform that exhibits multiple steps at several voltage levels. Further, ultra-capacitors may be electrochemical capacitors that may have a relatively high energy density when compared to common capacitors, typically on the order of thousands of times greater than a high capacity electrolytic capacitor. In addition, ultra-capacitors may have a variety of applications, such as in “energy smoothing” and momentary-load devices. Also, ultra-capacitors have applications as energy-storage devices in vehicles as well as home solar systems.
Other electronic devices that may use voltage balancing techniques for capacitors may be groups of large, specially constructed, low-inductance high-voltage capacitors banks that may used to supply large pulses of current for many pulsed power applications. Such applications may require accumulating energy over a relatively long period of time and releasing it quickly thus increasing the instantaneous power provided to the applications. Pulsed power applications may include electromagnetic Banning, Marx generators, pulsed lasers (especially TEA lasers), pulse forming networks, radar, fusion research, and particle accelerators. Further, large capacitor banks may be used as energy sources for the exploding-bridgewire detonators or slapper detonators in nuclear weapons and other specialty weapons. Also, banks of capacitors may be used as power sources for electromagnetic armor and electromagnetic rail guns and coil guns.
Voltage source inverters (VSI) are electronic devices that convert direct current (DC) to alternating current (AC). VSIs may be used in various applications such as computer power supplies, uninterrupted power supplies (UPS), High Voltage Direct Current (HVDC) power transmission, and electric vehicles. Further, voltage source inverters may be used in applications that have a DC power source, such as batteries or solar panels. In addition, a VSI may be used in Distribution Static Compensator (DSTATCOM) applications.
An electronic device such as a VSI, for example, may be constructed in several different configurations. Depending on a configuration, DC voltages across different components of the electronic device may drift from a reference voltage, and thus, may degrade performance. Voltage drift may arise due to minor effects such as capacitor leakage, unequal delays of other devices, presence of DC components in circuit current, etc. Imbalances in voltages across different components within the electronic device may also be present.
Techniques may be implemented to reduce voltage imbalances across different components (e.g. capacitors) in the electronic device. The components may be controlled to discharge and charge the device components such that voltages across the components are substantially balanced. Sensors may also be coupled to the electronic device to measure voltages to detect a voltage imbalance as well as to measure output currents.